1. Field of the Invention
The present invention relates to a phase deficiency display device of a thermal magnetic type molded case circuit breaker for protecting lines and electric load devices in an electric power system by breaking a fault current, such as overload, short circuit current and electrical leakage when fault current is generated on the power lines, and more particularly to the phase deficiency display device for the thermal magnetic type molded case circuit breaker capable of displaying a phase deficiency generated on the power lines.
2. Description of the Prior Art
As generally known in the art, a molded case circuit breaker is installed in a power distributing board of power receiving and distributing equipment provided in factories and buildings. In a no-load state, the molded case circuit breaker acts as a switching device for supplying or breaking electric power to a electrical load. In a load state, the molded case circuit breaker acts as an electric power breaker for breaking electric power supplied to the load from a power source so as to protect a cables of an electric circuit and devices of the load if large current exceeding rated load current flows due to fault on a load line.
Therefore, various kinds of molded case circuit breakers having various frame sizes, poles and operating manners are fabricated. Basically, the molded case circuit breakers have various elements including a mold case, a contact, a trip device, a switching mechanism, an arc chamber, and a terminal.
Hereinafter, the above elements of the molded case circuit breakers will be described.
The mold case includes a case and a cover, which are made of insulating material. The mold case forms a container in order to receive various elements in such a manner that elements installed in the case and each element of phases (so called pole) is insulated from each other. The mold case protects persons from an electric shock derived from internal elements in the mold case and has a structure capable of preventing impurities from penetrating into the mold case.
The contactor includes a movable contactor and a stationary contactor. The contactor is installed for each pole so as to open or close an electric circuit.
The trip device trips the switching mechanism when the device detects over-current or short circuit current.
The switching mechanism drives the movable contactor when the trip device trips the switching mechanism. In addition, it is possible to manually drive the movable contactor by using the switching mechanism. The switching mechanism can automatically perform a switching operation.
The arc chamber extinguishes arc created between the movable contactor and the fixed contactor.
The terminal is assembled into each pole of a power source part and a load part so as to connect an external electric wire or an external conductor to an internal conductor.
Tripping device is installed in the molded case circuit breaker so as to detect over-current The trip device is classified into a hydraulic-magnetic type trip device using viscosity of silicon oil, a thermal magnetic type trip device using a bending characteristic of a bimetal and having fixed and movable cores, and an electronic type trip device using a semiconductor device.
The thermal magnetic type trip device performs a time-delay trip, in which a heater generates heat caused by over-current and the bimetal is bent due to the heat, thereby automatically breaks the electrical circuit, and an instantaneous trip, in which the fixed core attracts the movable core when relatively great over-current is applied, thereby automatically shutting off the electric circuit. That is, according to the time-delay trip, the molded case circuit breaker is operated to a breaking position due to a bending action of the bimetal. In addition, in case of instantaneous trip, the fixed core attracts the movable core based on the principle of an electromagnetic suction, thereby the molded case circuit breaker is operated to a brealing position.
As shown in FIG. 1, such conventional thermal magnetic type molded case circuit breaker includes a mold case 1, a bimetal 2, which is bent in proportion to a heat of a heater 3 when current is applied thereto, first and second shifters 4 and 5, which are coupled to an upper end of the bimetal 2 and horizontally movable in proportion to a bending degree of the bimetal 2 when over-current is applied thereto, and a shifter lever 6 inserted into through holes formed in the first and second shifters 4 and 5 by interposing protrusions therebetween in such a manner that the shifter lever 6 is rotated at a predetermined angle according to the movement of the first and second shifters 4 and 5, thereby rotating a latch of a driving section (not shown) so as to shut off electric power. Reference numerals 14 and 7 represent a connection bar and an auxiliary device frame, respectively.
Hereinafter, an operation of the conventional thermal magnetic type molded case circuit breaker will be described.
Firstly, when rated current is applied, the heater 3 generates heat, causing the bimetal 2 to bend.
At this time, the first and second shifters 4 and 5 coupled to the upper end of the bimetal 2 are horizontally moved in a same direction as a bending direction of the bimetal 2.
As mentioned above, the first and second shifters 4 and 5 are formed with through holes, and the protrusions of the shifter lever 6 are inserted into the through holes.
When normal current is applied, the bimetal 2, which has been bent at a predetermined degree due to heat generated from the heater 3, moves the first and second shifters 4 and 5 in the bending direction of the bimetal 2 corresponding to a bending distance thereof.
At this time, if the phase deficiency occurs at one phase current of three phases (R, S and T phases) alternating currents, electric current flows to concentrate the remaining two phases, so over-current occurs, thereby causing damage to a load connected to the conventional thermal magnetic type molded case circuit breaker.
In addition, since current does not flow through the phase occurred phase deficiency, the heater 3 for the phase cannot generate heat so that the bimetal 2, which has been bent, recovers its initial shape. At this time, if the bimetal 2 is developed in a direction opposite to the bending direction thereof in order to recover its initial shape, the shifter 5 also moves in the direction opposite to the bending direction of the bimetal 2. In addition, the shifter lever 6 is rotated in the bending direction due to the movement of the shifter 5 so that an end portion of the shift lever 6 rotates the latch of the driving section (not shown), thereby breaks the circuit.
In addition, an accessory device is coupled to a body of the conventional thermal magnetic type molded case circuit breaker. When an error occurs in a load or a power source part due to fault current, a detecting section and a switching mechanism are operated so as to perform a trip operation for disconnecting a contact of a contact section. At this time, the accessory device is operated together with the detecting section and the switching mechanism, thereby displaying a signal to an exterior.
However, although the conventional thermal magnetic type molded case circuit breaker having the above structure can display the trip operation caused by fault current, such as over-current and instantaneous current, to the exterior, the conventional thermal magnetic type molded case circuit breaker has no display function for the trip operation caused by the phase deficiency.
When the phase deficiency occurs at one of three phases (R, S and T phases), heat is generated from lines of the load part, causing a remarkable loss of the lines. However, according to the conventional thermal magnetic type molded case circuit breaker, it is difficult to recognize the reason of the trip operation. That is, it is difficult to know whether the trip operation is derived from fault current, such as over-current and instantaneous current, or from the phase deficiency, so it is impossible to rapidly deal with the phase deficiency